Sunday, 23 February 2014

Poisonous Writing

Last time I looked at the rather unsavoury ingredients once used in everyday trades. A visit to the British Library in London gave me the opportunity to see some of the illuminated manuscripts of yesteryear. Despite the age of these documents the colours remain quite wonderfully preserved and got me wondering about the recipes to produce the different colours.

It must be said the recipe very much depended upon what was available at the time and thus changed depending upon where the monks and their quill pens were based. I admit I have chosen the worst possible blend in each case, although even the least harmful could never be described as palatable.

In nature red is a warning colour, used by animals to suggest toxicity. When it comes to red ink the same could be said regarding some of the ingredients. Lac is derived from the excretions of certain insects, gathered from the bark of the tree and treated to produce the red colour. It is the same substance which produces shellac. In Britain we were more likely to have used red lead, not exactly the safest of products, or vermilion, found in nature as cinnabar and known to chemists as mercury sulphide.

Saffron will produce a delightful yellow pigment but, pound for pound, the most expensive foodstuff on the planet would be unlikely to be wasted making yellow. Again a mineral solution proved more cost-effective, with limonite being the optimum choice but could not be guaranteed to produce the same shade of yellow every time. This was not the case with orpiment, which was used until the nineteenth century but did have a downside in being incompatible with other pigment bases and, worse still, being toxic in the extreme – a clue found in the chemical name of arsenic sulphide.

At last based on something most of us will have heard of. Verdigris is the coating which forms on the surface of copper over time. It will occur naturally, although boiling copper plates in vinegar accelerates the process. Verdigris is not always the same compound, there are several which are known as such, but all have one thing in common, the element copper making them extremely toxic.

Of course the classic is woad, the plant which Britons once used to paint themselves blue. At last a plant which may actually have beneficial properties, one thought to offer some prevention against cancer. On the minus side the root is used in Chinese herbal medicine and long-term use can do damage to the kidneys. Perhaps this explains why blue pens have always been the most popular?

Not exactly a common colour in illuminated manuscripts but certainly a necessary one. Chalk was the obvious ingredient but that did only sit in suspension and will only prove a temporary solution. Most often the ominously-sounding white lead was used. Correctly lead carbonate was created by popping lead sheets in vinegar to corrode them, then covering the result in dung to lock in the carbon dioxide and complete the process. Such white lead paint was used on the wooden hulls of Royal Navy vessels to prevent infestations of marine worms. While the use of the colour is not directly toxic, the process required to achieve this is undoubtedly so.

Usually carbon as a result of burning, such as lampblack, charcoal, bone, etc would prove difficult to use. Most often the black pigment was created by boiling iron in vinegar, the result then mixed with an extract from oak apples or galls.

Here the monks used powdered gold which was mixed with egg .

Exactly the same as gold, the precious metal was reduced to a powder and mixed with egg. Sometimes tin replaced silver for the same result.

As I researched and wrote this I was reminded of those irritants at school who would lick the (pointed) end of their pencil before writing. They would not have lasted long as medieval monks.

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